1. Field of the Invention
The present invention relates to a power feeding device, a power receiving device, and a wireless power transmission device.
2. Description of the Related Art
A power feeding technology which supplies power without using a power cord, that is, a wireless power feeding technology has attracted attention. Since the wireless power feeding technology is able to supply power from power feeding equipment to power receiving equipment in a non-contact manner, it is expected to be applied to various products such as transportation equipment including trains and electric vehicles, household appliances, electronic equipment, wireless communication equipment, and toys.
In devices to be used in the wireless power feeding technology, magnetic coupling between a power feeding unit such as coils on the power feeding equipment side and a power receiving unit such as coils on the power receiving equipment side is important in order to efficiently transmit power from circuits on the power feeding equipment side to circuits on the power receiving equipment side.
FIGS. 22 and 23 illustrate an example of a wireless power transmission device by electromagnetic induction. In FIG. 22, a power receiving device 286 is compact electric equipment. In FIG. 23, a power receiving device 306 is an electric vehicle. In wireless power transmission devices 200, 300, primary coils L1 constituting power feeding units 283, 303 of power feeding devices 284, 304 and secondary coils L2 constituting power receiving units 285, 305 of power receiving devices 286, 306 are respectively opposed to each other, so that power is supplied from the power feeding devices 284, 304 to the power receiving devices 286, 306. Since each of the primary coils L1 and the secondary coils L2 is respectively located at one position of the power feeding devices 284, 304 and one position of the power receiving devices 286, 306, it is difficult to supply power to the power receiving device 286, 306 in a state having a good transmission efficiency while having a degree of freedom in the arrangement of the power receiving devices 286, 306 and the power feeding devices 284, 304.
From the viewpoint of the arrangement of the power receiving device, Japanese Unexamined Patent Application Publication No. 2005-110399 discloses a power supplying system in which a plurality of power transmission-side coils and power reception-side coils are respectively provided in power transmission equipment and power receiving equipment so that a user is able to arrange the power transmission equipment and the power receiving equipment without worrying about their positional relationships.
In the above-described power supplying system, a circuit that outputs a signal is provided. The circuit outputs a signal so that among the plurality of power transmission-side coils and power reception-side coils a power transmission-side coil and a power reception-side coil of which power transmission efficiency is best can operate.
Further, Japanese Unexamined Patent Application Publication No. 4-317527 discloses a non-contact charging device. The non-contact charging device includes an electric equipment main body having a secondary coil of a loop shape and a charging unit that charges a storage battery by an output of the secondary coil; and a charger which has a box body made from a magnetic material that retractably houses the electric equipment main body inside thereof, a primary coil of a loop shape which is wound along an inner peripheral surface of the box body, and a charging circuit that supplies a primary current to the primary coil, and supplies power to the charging unit of the electric equipment main body.
On the other hand, from the viewpoint of power transmission efficiency, Japanese Unexamined Patent Application Publication No. 2009-268248 discloses mobile equipment of which a rear face is curved, and a charging base of which a bottom face is curved so that power is easily transferred from the charging base to the mobile equipment.